1. Field of the Invention
This invention relates to piston and oil scraper ring assemblies of the type employed in engines, compressors and other machines, and more particularly to an improved piston and scraper ring assembly having means for providing more efficient and complete return of oil from a cylinder wall to the oil sump.
2. Description of the Prior Art
The pistons movable in cylinders in internal combustion engines, compressors and other machines (hereinafter referred to generally as engines) are generally equipped with a scraper ring mounted in a groove in the piston and intended primarily to restrict the passage of oil between the crank case and the working chamber of the piston. During every piston stroke, the ring scrapes the oil off the walls of the cylinder and recycles it to the crankcase by way of the gap between those mutually adjoining ring and groove surfaces which are leading during that stroke of the piston, and then by way of orifices, generally in the bottom of the groove, leading to the crank case via the interior of the piston.
During each stroke this oil recycling circuit is open due to the pressure of the piston on the ring until the time during the second half of the stroke when inertia forces arising from deceleration of the piston throw the ring on to that side of its groove which is leading at the time. This interrupts the oil recovery circuit for the remainder of that stroke, and at each dead center the ring accumulates, against its leading side and against the cylinder, a band or film of scraped oil which escapes from the recycling circuit. The band of oil deposited at the top dead center has a considerable effect on the oil consumption of an engine, and the present invention is concerned with recovering at least some of this band of oil at the top dead center position.